Category Archives: Microphones

New Music- “Here You Are” by Spinster

Here’s a video I worked on for Spinster in Chattanooga. Capture was done in six tracks- no overdubs- using my Sound Devices 664. Look closely and you’ll see the Watts Polyribbon being used on Amelia’s vocals. A very slight touch of Universal Audio EP34 tape delay was added to the vocals.

 

Their Facebook page is Spinster@callmespinster

Polyribbon Photos

My good friend Sandy Andrews happens to be a commercial photographer in Columbia, SC, so when I travelled there for the IPMS Nationals, I brought the Polyribbon with me and we headed over to his studio. These shots are the result. Sandy does catalog work for some very high-profile clients, so he’s got the chops (and the equipment, and the space) to shoot some really nice images. Hopefully you’ll see these in Mix Magazine someday!

While this looks like a vintage mic, everything in it is brand new. Les Watts, the designer, is a little bit neurotic when it comes to accuracy and quality… everything on this mic is executed with tolerances that are extremely close, which makes building these very time consuming and expensive. The banding around the headbasket is hand-filed brass that is then nickel-plated, the edges of the grille are all soldered. The frame that holds the magnets are assembled with dowel pins instead of screws, since screws have microscopic gaps that affect the magnetic reluctance of the frame. The wrinkle paint finish on the body is a custom formulation that Les had made just for this mic.

This mic has plain knobs because Les had trouble finding a laser engraver who could maintain the proper accuracy. Since each knob has to be handmade, a screw-up by the engraver would cost hours of work, so they have to be extremely careful. We’ve since located a supplier, so the new mics will have knobs with laser engraved and infilled legends. A simple silkscreened legend is much easier to make and looks the same at first, but these rub off after a few years. Les builds these with an expected lifespan in excess of fifty years, and all materials are selected for longevity.

These mics really need to be seen- and heard- to be appreciated. If you’re interested in acquiring one for your studio, contact me for a demonstration!

_5713_desatbg_5717_desatbg

Watts Polyribbon At Work

Here’s a link to a project that I worked on recently. The band is called Spinster… they’re three sisters with classical music training. One lives on the west coast, one in Chattanooga, and one in Costa Rica, so they don’t get to play very often. We recorded a series of three songs this summer, they’ll eventually be posted on YouTube

We set it up as a live multitrack recording with no overdubs, so it’s very much a live performance video.  It’s also the first chance that I got to use the Polyribbon. I used it on lead vocalsfor two songs… very smooth. And just to change things up a bit, we tried it on the upright bass for one song, which gave a teriffic sound. No EQ was used on the Polyribbon signal.

Recorded on the Sound Devices 664. It was mixed using the Harrison Mixbus 32C using Universal’s EMT 140 plate reverb on the vocals. Instruments are pretty much dry. Noise reduction and mastering via Izotope RX Pro and Adobe Soundbooth.

Hopefully I can get them in the studio this summer for an album. Enjoy!

 

dsc_1503dsc_1516dsc_1523

A Ribbon Microphone- Design 001, Rev A

Since I have to give away the Austin Ribbon Mic that I built, I decided that I wanted one of my own. I purchased raw materials for four more ribbon mics and have been working diligently on another mic. It isn’t completed yet, but I’ve done enough (and it looks good enough) that I can show off some preliminary photos.

My progress so far on ribbon mic no. 2, which incorporates a large number of design changes from the previous mic.

This microphone is similar to the Austin ribbon, but it’s a completely new design inside. The body style is similar, and I’m using a similar motor frame of clear acrylic plastic with drilled vent holes as a frame for the motor, but that’s where the similarity ends.

The Austin mic sounds great, but my outboard preamps are… well… let’s just say they aren’t top-of-the-line models. (Except for my lovely pair of VP26 pres from Classic Audio Products of Illinois, but I don’t have a Lunchbox yet to mount them in. I’ll get them racked one of these days, but the studio needs to generate some income first.)

So as a result of my gear, I’m having to crank the preamps up a good bit on the Austin mic. It sounds great on a source like an acoustic guitar, but for voice it requires a super clean preamp. (The Crest preamp that I recently purchased is a significant improvement.) This new design is an attempt to increase the output a little so that I can get a better signal with more common equipment.

My redesigned ribbon motor frame with magnets in place. A central groove is milled in the plastic for positioning the ribbon. The magnet spacer is just a piece of 4mm aluminum.

I’ve redesigned the motor frame using magnets that are slightly larger at 5mm x 10mm, and a ribbon that is slightly narrower, about 3.5mm. It’s counterintuitive, but narrower ribbons have a higher output. I’m using a 2.5 micron aluminum ribbon foil. The plastic frame is machined with a slot down the middle to hold the ribbon, and a pair a milled aluminum clamps to hold the ribbon in place. I didn’t want to use copper here because of galvanic reaction concerns. Everything is held in place by 4-40 capscrews, which are magnetic & will probably be a pain in the ass to install, but we’ll see. I’m waiting until most of the work is completed before I install the magnets and the ribbon, since the magnets will attract bits of ferrous crud in handling & the ribbon is so very fragile. That’s why they aren’t in place in the photo above.

The frame installed on the motor mounting tube. The ribbon clamps have been machined and are in place. I’ll probably secure the wiring with a dab of glue once the ribbon is installed.

Another difference is in the motor mount. I’ve built a secondary can that slides inside the mic body from a small piece of galvanized fence tube with a fender washer silver soldered to the top. This will shield the transformer almost as well as a Mu-metal can, and it makes a sort-of “mic-within-a-mic.” This same type of construction is used with great results on the Electro-Voice RE50 reporter’s mic, one of my favorites. This sub-assembly is isolated from the outer shell of the mic with a wrap of foam. This will be of limited benefit, since a ribbon mic is never handheld except when used as a prop in music videos. But I did want some way to take the mic apart and put it back together as a single unit… the Austin design has the motor pressed against the mic body with strips of neoprene foam. It works well, but isn’t ideally suited to taking the mic apart. I expect to do that a bit more with this mic, as I experiment with things like silks around the ribbon or waffle-plate resonators.

I’m calling this one Revision A, since I redesigned & rebuilt the mount to correct a grounding problem. I’m already working on Revision B, which will be largely similar except for the ribbon clamps and  more space at the bottom of the frame for mounting the motor with screws. (Revision A’s mount is secured with glue.) I’ve got some other ideas to try with magnet sizes and frame designs, but I need to give these an extensive listening test first.

I’m still waiting on a few parts… the transformer and the XLR, mainly… but I hope to have this project finished soon, and I’m anxious to hear the results. In the meantime, I’ve started milling parts for another one.

The semi-completed shell. I still need to machine the brass cap at the bottom and mount the XLR connector. Overall length is just about six inches.

The cost for this project is fairly high, mainly due to the amount of time that is spent in construction. If you add in the cost of the machine tools, the cost goes from fairly high to astronomical. I’m using a benchtop drill press, a 7×10 Chinese lathe and Taig milling machine to make these. All three have been essential for various parts of the work. While it would be theoretically possible to build a mic with hand tools, it is a lot easier to get good-looking results in less time with some heavy machinery. (If you lack the tools, Rick Wilkinson’s Austin ribbon mic kit is highly recommended, see my previous post.) And actually, my setup is pretty minimal… I could use a larger lathe & a CNC mill for faster and better results… but now we’re talking about an investment that would require going into business as a mic manufacturer, which isn’t my intent. These are experiments. I’ll probably make a few available for sale at some point, just to recoup some of the cost of the parts. And I expect the price on them to be rather high, just because they take so very long to make. But these are primarily built for my own satisfaction. It won’t hurt the resume, either.

I owe a great debt to Rick Wilkinson and Les Watts (former mic designer with Shure and EV) for teaching me a large majority of what I know about building ribbon mics. Their help is very much appreciated.

UPDATE: I’ve very nearly completed this mic… I recut an existing XLR connector on my lathe, so now it fits the microphone. The magnets were fitted to the frame, and I mounted a 2.5 micron ribbon yesterday. I’m guessing it’s about 3.6 mm wide. It’s a nice, tight fit. The ferrous capscrews were a pain in the ass, but not impossible to deal with.

The ribbon motor completed, with magnets and ribbon installed. Using 2.5 micron ribbon material is much easier than signwriters leaf, though it’s still not a simple process to install.

Now I’m just waiting on the transformers to arrive. These will be a special custom-wound ribbon transformer that should meet or exceed specifications from the usual suppliers. Unfortunately, it probably won’t arrive in time for the DIY seminar… I was hoping to have this working before then.

This mic comes with a custom walnut mic box that I had built by a local cabinetmaker. Nothing on this mic is sourced from Chinese suppliers… that sort of thing is easy enough to get from just about anywhere these days. If nothing else, this mic will be different from the common stuff that is so prevalent these days.

UPDATED UPDATE: When I went to use this mic recently, I discovered that the glue had failed on one of the magnets and it had separated from the frame, bringing the two together and turning the carefully-placed ribbon into aluminum dust. So while this is an easy-to-build example of how ribbon mics work, it isn’t the best design in terms of longevity.

My new design incorporates a steel frame rather than plastic. This is slightly better from a magnetic perspective, and it’s naturally stronger for threads, etc. I’m thinking of trying a frame made from small pieces of 1/4″ square steel. Machining from solid would be a possibility, or I could even get crazy and go to the blacksmith shop and forge something… I was formerly a full time blacksmith and still have access to some large and heavy tooling. And I’m pretty sure that nobody else is hot forging their ribbon mic parts.

But the key design element will be a small notch to hold the magnets apart. I should have done this before, as it could be incorporated into my earlier frame design. It’s yet another thing to put on my long list of projects.

The finished mic in its custom-built, handmade walnut box.

Austin Ribbon Mic Completed

The completed Austin ribbon mic. This one will be given away at the Producer’s and Engineer’s Summit at Welcome To 1979 in Nashville, coming up in November.

Here’s a look at my Austin ribbon mic, I completed it yesterday. Building this mic certainly was actually really easy, except for one part… installing the ribbon in the frame. I had to do this several times… six, to be exact. I  had various problems. One, for example, didn’t show it’s ugly head until I’d completed an installation… tiny tears all along the edge of the ribbon. I learned they were caused by the ruler I was using, which had a cork backing that was set slightly behind the ruler’s edge. This small unsupported space allowed the foil room to stress and tear. I corrected this by using a length of rectangular aluminum as a straightedge, this pressed down on the foil right at the cutting edge.

Another problem I had was corrugating the ribbon. I was trying to protect the ribbon by corrugating it with the release paper on the top and bottom, but doing so a) causes the ribbon to curl up, and b) makes the corrugations shallower. If the ribbon isn’t sufficiently corrugated, it is extremely difficult to get it tensioned properly. The tension is important… the ribbon can neither sag in the frame, nor should it be too tight. I had the latter problem, and the ribbon developed a longitudinal curl, so scratch that ribbon.

But thanks in no small part to Rick’s patient support via several emails, I finally got one in. It wasn’t perfect… it could be centered just a hair better… but it looked ok, so I closed it up and finished the mic.

And considering everything, it sounds quite lovely. The last time I used a ribbon mic was 25 years ago, when I did my thesis recording using a pair of RCA TK77’s that the university owned, so I don’t have much of a frame of reference, but it seems to have a nicely balanced frequency response. From what I understand, construction errors show up as poor highs or lows. I don’t have a frequency analyzer set up yet so I can’t give any numbers, but my subjective analysis says “nice.” Now, like all ribbons, the output is rather low, and I did my testing using a rather crappy mic preamp. On voice, one has to crank the gain up quite a bit, and this gave me a lot of preamp noise. For someone who is a low talker, this wouldn’t work. But I got a rather useable level on my acoustic guitar.

Again, I can recommend Rick’s kit quite highly, especially if you’ve never built a mic before. He’s done everything that can be done to insure a good outcome, and the one I built certainly worked out well. That’s not to say it’s simple… you need patience, and good, steady hands will help as well. But I’ve already got parts here to build four more for myself!

The Austin Ribbon Mic

I recently received an Austin Ribbon mic kit from Rick Wilkinson (Rickshaw Records) out in California. Unfortunately, I can’t say I’m the proud owner… this mic is going to be built and given away as a door prize at the DIY panel at the Producers and Engineers Summit at Welcome To 1979 in November.

I haven’t finished the build yet, so I can’t give a complete review of the mic, but I can make some comments about the kit and the resources that come with it. Building a ribbon mic is not that complex- IN THEORY. It’s just a thin metal ribbon suspended between two magnets. There isn’t much electronic inside the mic, just a transformer. The design has been around since the 30’s.

The theory is simple. But like most things, it’s the Devil in the details. You can find articles and instruction on the web for free. And that’s what I started to do years ago. I got halfway through the project and shelved it… there wasn’t enough detail for me to be successful.

Or you can spend some money and increase your chances. Rick sells plans for ten bucks, or his ribbon kit for $275 with a Cinemag transformer. (There is a less expensive version with a stock transformer, and I understand the stock transformer is exceptionally high quality. It’s sold out right now, but should be available again shortly) Rick sent me a kit with a Cinemag transformer, so that’s the version I’m reviewing here.

The kit itself is extremely well done. The mic tube is powder coated brass, 1 1/2″ diameter, and exactly machined. All the holes are already drilled, so you don’t need a drill press. The motor frame (a critical part) is a machined piece of plastic. The fit was perfect. I especially liked his design… I designed my own once, and it was a cumbersome mess. Ricks is elegant, simple, strong, and works well. (some folks claim that metal frames are superior. Perhaps they are… I’m not sure… but I think that at least part of the reason behind this claim is that’s what is available from China.)

The greatest value for me, though, is Rick’s instructional materials. When you buy a kit (or his plans), he sends you a link where you can download  PDF instruction manual and several videos where he goes through the process of building a mic. These videos are really helpful, especially when it comes to corrugating and installing the ribbon.

Commercial mics use ribbons that are anywhere from 5 microns to 1.8 microns thick. The ribbon material that Rick supplies is about 0.8 microns. (Thinner ribbons increase high-freq sensitivity.) This is similar to “imitation silver” guilding leaf, it’s readily available on the internet. I’ve bought some from Hobby Lobby before and tried to cut a ribbon from it. I can say without hesitation that it ain’t easy. But that’s the beauty of these videos. Once you see someone doing it, you understand the method better… much better than just reading about it. And you can see that it is possible to make a well-functioning ribbon from scratch, but understand that it’ll take some practice. Even breathing can cause a cut ribbon to fly off your bench. So be ready to make several practice ribbons before you get one correctly made and mounted in your mic frame. And if you just can’t get it, there is an internet source for commercial ribbon foil now. A company called Lebow sells pure aluminum foil in a variety of thicknesses, including 1.8 and 2.5 microns. This would be vastly easier to handle, but it’s also vastly more expensive at $25/sheet. (There may be other sources as well, but this was the only one that I could find. I ordered two sheets to use in my own mics, but they aren’t in yet.)

Ribbon-making details is a big advantage of his instructions, but it isn’t the only one. For example, I learned that you can use a brass footrail cap on the bottom of your mic to hold the XLR connector. These things are nice, solid castings, and if you shop around, you can find them at about $5 apiece. (I wish I’d thought of that.) Circular Switchcraft connectors fit well in these caps.  This would be a good solution for any tubular-bodied homebuilt mic.

The videos do have a slight downside. You have to remember that Rick has built a lot of mics, so some of the things he does in the videos look easier than they will be to folks like you or I. It’s really difficult to explain the things that practice teaches you. But I’m pretty sure that I’ll have a working ribbon mic once the dust settles… I’ll keep you posted.

UPDATE: I finally got up the nerve to install the ribbon today. It worked on the second try, which really isn’t bad. I’m pretty sure that my success with this is pretty much due to Rick’s instruction. Like I said previously, I’ve tried this before and failed miserably. Seeing it done (in a video) makes all the difference.

A just-placed ribbon in the motor frame. This job requires lots of patience, but it can be done.

That is not to say, however, that it was easy. The foil is the definition of flimsy… if it were any thinner I think it’d fly off my bench because of the rotation of the earth. Using the more expensive 2.5 micron foil should be easier (though I expect still no picnic), and that’s what I’m planning for my own ribbon motor frames. (I figured this one should be made as a stock kit, in order to give a fair review.) There will be some slight differences, like slightly thicker magnets… I’m still in the design and prototype phase. But if they work, it’ll be fun to try some design variations like waffle plates (resonators) and silks.

More Mic Mods- the ADK SC-2

Because of my posts about modifying microphones, I recently received an invitation to visit a proper mic designer. Les Watts is an engineer who worked  for some VERY prominent microphone companies… I’m fairly certain that at least one of them is in your locker right now.

Les lives about a three-hour drive from me, so I went by for a short visit recently. It was, of course, extremely educational. I brought along a pair of mics that I had doctored, and we tested them using his calibrated setup.

The ADK SC-2 small-diaphragm condenser microphone. The stock mic is on top, the modified capsule is shown on the bottom.

One of the things that I learned… or rather confirmed… on my trip is that real microphone design is a very slippery fish. A microphone is a true “complex system…” one small change affects a whole host of other factors. The mod that I did (not so much a design as a “I-wonder-what-will-happen-if-I-do-this” sort of affair) was to cut away the area in front of the mic diaphragm, leaving the area more open and less restricted by the grille and metal in front of the diaphragm. It turns out that the “cup” shape that is created by the area that I cut away forms a high-frequency resonator, which I’ve essentially removed. Sometimes this  is a good thing, sometimes not.

The ADK capsule shell disassembled for modification. As you can see, a small-diaphragm capsule is a fairly simple affair with just a few parts. An important part that you can’t see is the spacer ring that lies between the diaphragm and the backplate. It’s a simple washer made from thin mylar film that looks much like diaphragm material… about 6 microns thick.

Assembling the modified SC-2 capsule. Any dust trapped between the diaphragm and backplate will ruin the capsule. It took a few tries.

Consider the following two mic capsules. These are for some ADK SC-2 small-diaphragm condensers that I have. I had an extra pair of dead capsules, so I figured I could play around with these without much risk. (I did get them working again) The only change was removing the cage at the front of the diaphragm, lowering the height of the sides to about 2mm, giving the edges a gentle radius, and using a finer brass screen in front.

I did a quick recording of both modified and unmodified capsules. On guitar, I really couldn’t tell much difference at all. But Les’ test rig tells a different story. Take a look at the following response curves:

First off, you should ignore the huge rise below 200 Hz, which is due to proximity effect of the test setup. What I found interesting was the rise in response of the stock capsule centered around 8kHz. Les told me this is a pretty typical Chinese mic response. Looking at the lower of the two curves, we see that modifying the headshell does even out this rise, and gets us a slightly extended high end response…  but it also introduces a pretty deep notch at around 6kHz. This notch is present in the unmodified capsule too, but to a lesser degree. This could be why the capsule shell was designed the way it was.

Another take-home lesson from my trip is the need for a better testing setup at my studio. Remember, on guitar I could make out very little difference in the two mics. (I don’t have golden ears, but I have done a lot of listening.) Perhaps another recording of something with more transients, like a snare, might be more revealing. Again, according to Les, notches in a response of this sort are very difficult for the average person to identify in listening tests. What I could really use is a setup that’s similar to his.

Les uses ARTA software, which is available as a download. His calibration mic is an extremely expensive calibrated B&K, and his loudspeaker (for generating the test tones) is custom-built. It might be possible to get a similar setup at my studio using some equipment that I already have. It won’t have the accuracy that Les’ system does, but I believe I can get something put together that will show the relative changes of a modified vs unmodified capsule. I’ll need a few things, like a Windows computer… I’ve been a Mac guy for many, many years. (Our first Mac II at the recording studio gave us a HUGE advantage, enabling us to design several cassette and CD releases in-house. Back then, graphics ability was a big deal that only Mac folks could do… nowadays, not so much!)

So I’m currently on the hunt for another inexpensive computer (this will be #4) that I can use with ARTA as a dedicated test machine. My son’s old Dell doesn’t seem to want to generate any video, but I may yet be able to get that one going. If not, it’s off to the thrift store for some computer shopping.

I’ll also need a calibration mic and a speaker. The mic might not be too bad, and I may be able to borrow or beg this one. The speaker will be a little harder, though I do have a pair of KRK5s that might at least get me started.

Lots more to come… stay tuned!

Small diaphragm Condenser Modification Results

Last week I sent the small-diaphragm condenser mics from the post below to a friend in Nashville, John Billings. John’s been working in Nashville for years as a session bass player, and  has a very nice studio. I only wanted his general impression, but he went the extra mile and set up a quick A/B test during a recent session. Here’s what he had to say:

First off WOW, thanks for some toys to play with! Here’s what I’ve got so far:Did a session the other day. One song was just these mics out in the room, capsules aligned and secured. You can hear a distict but subtle difference. The mod is much smoother, whereas the stock mic seems to have a significant rise. The other song was a drum corp type of thing, just snare rudaments. Mics placed a few inches over the head, inch or two inside the hoop. I much prefer the mod, though if you need something hyped for top end, the stock mic might be the better one to go to. The mod is smoother, not brassy. Preamps were Yamaha, very neutral. No compression, straight to my SSL AD, 44k 24bit.

The snare mic setup at John’s studio. John Billings photo

I’ve been meaning to upgrade my WordPress account for quite awhile now, but John’s efforts gave me the final push. Now I can post these files here so you can hear the results and judge for yourself. First, the snare drum solo using the stock, unmodified CM90:

drum corp- Snare 1 N Stock

And next is the modified mic:

drum corp – Snare 1 N Mod

Now the same two mics placed further back as a room mic on a full drum kit. Again the stock mic is the first sample:

Drums Room Nady STOCK

And now the modified mic:

Drums Room Nady MOD

John’s studio is equipped with Genelec monitors, so he’s able to hear things very accurately. I listened to these samples on the best headphones that I have, a pair of  AKG 271s, and on my KRK Rokit 6 studio monitors as well. I noticed a slight drop in level on the modified track, and raising this a touch in Mixbus gives more closely-matched tracks in terms of level. (As you probably know, you’ve got to have levels very close when doing A/B comparisons. In blind tests, people always select a source that’s slightly louder as the better track. )

I tend to agree with John. I’m hearing an overall improvement in freq range, with a touch less upper-midrange and an increase in overall smoothness. It’s a subtle improvement… but when comparing them side-by-side, it’s noticeable.

But something that I always find surprising is the fact that really, these mics aren’t all that horrible right out of the box. I’m showing my age here, but in my studio days you couldn’t even approach this kind of signal for less than three or four C-notes. Sure, the quality control isn’t there… for example, the tiny screws that hold the mic body in place are chewed up and look like they were forced together at the factory… but I can’t really complain given the list price.

In order to make some proper mic comparisons, I’m going to have to buy a proper reference mic, so I’m currently selling some excess gear to buy a Neumann KM184. I’d rather have a vintage KM84, but they’re just much for my current budget to bear…maybe someday. And I’m also on the hunt for an affordable BV107 (or perhaps a suitable equivalent) mic transformer… I want to experiment with a transformer-balanced version of the above mod.

A Small-Diaphragm Condenser Rebuild

Back in my studio days, we had a pair of AKG 451s, and we thought we were hot stuff. The 451 is a beautiful microphone, and we’d been using them for several years with great results… my favorite job for these was stereo drum overheads. Then one day Robert brought in a pair of these tiny little microphones… Neumann KM84s. We set them up right next to the 451s as a pair of drum overhead mics, and switched back and forth to compare them and… wow… the difference was amazing. The KM84s sounded every bit as bright as the 451s, but smoother, as if they had more “air.” They quickly became my favorite mic.

Sadly, they went away when the studio closed. One got stolen… their tiny size makes them easy to pocket. And they were pricey even 25 years ago. But I’ve wanted my own KM84 ever since,  even though I don’t really “need” one. And the price has gone up since then… Neumann no longer makes them, their current model is the transformerless KM184. Some have said that the older KM84 is the preferred mic, as these are said to be “warmer” and “smoother” in their sonic character.

KM84’s can typically be found used for about $1200 or so. I still want one, but I can’t really justify spending that kind of cash on a mic unless it’s going to generate the same amount in revenue. (I did spend that much on my shotgun mic, but I use it on every shoot. A KM84 would mostly be useful on location as an interview mic.)

The Nady CM90 disassembled. I understand these are pretty much identical to a number of inexpensive small-diaphragm condenser mics available, like the MXL603.

I can, however, afford a Nady CM90. This mic is one of the thousands of Chinese clones that have flooded the market. It uses a capsule that is supposedly a copy of the Neumann KK84 design. The circuitry is derived from a Schoeps CMC6 transformerless amplifier. Nearly identical to the Nady CM90 is the MXL603, Apex 180, CAD GXL 1200, Cascade M39, and others. Some folks have reported that there is a difference in the diaphragm thickness… the Nadys have diaphragms that are 3-microns thick,  and MXL603s have 6 micron diaphragms. Personally, I can’t tell. I bought the Nadys because they were only $35 each from B&H Photo, and if I totally ruined them, it would be less painful.

Arrows show the new capacitors.

Typical circuit improvements are the replacement of some capacitors, changing ceramic types with polyester film types. Face it, at $35 you can expect to see the cheapest components that’ll work in mics like these. I switched out three, using some parts I had on hand. The values are the same, it’s just the cap types that are different.

A side note: I didn’t come up with the actual number-crunching engineering to figure out the electronics. There is a small community of microphone builders on the internet (examples HERE and HERE) who, thankfully, are willing to share their experience and knowedge. A few of these folks actually did design work in the factories… it’s a real treat for sound geeks like myself to have access to these people. Without their help, I’d surely have a pile of dead mics as a result of my experiments, so I have to express my gratitude to these folks.

Increasing the back vent area with my Taig milling machine. (Taig tools are the perfect size for machining microphone parts, BTW.)

The next modification was to the back vent area. As I understand it, (from Michael Joly of OktavaMod) decreasing the back vents increases the high frequency (HF) response of the mic, and these are known to exhibit a typical HF “peakiness.” Even though the Nady probably didn’t need it, (there are more back vent slots on the Nady than on the MXL 603)  I fired up my trusty Taig milling machine and cut away the ridges in the back vents. I cleaned up razor edges with a small file and replaced the screen.

The other reported problem with these mics is the capsule mount. Again according to Michael Joly, the diaphragms on the chinese clones are set back into the body of the mics about 5mm, where the KM84s diaphram is positioned much closer to the top of the mic. That 5mm ridge around the diaphragm is enough to cause all sorts of HF problems. So I very carefully disassembled the capsule, chucked the shell up in my lathe, and shaved down the pocket. I also took the extra step of beveling the sharp edges, making it look similar in shape to the KM84.

Parting off the face of the capsule shell in the lathe. The brass is a little bit thin and easy to scratch, so I wrapped the shell with masking tape. It machines beautifully, though. This operation could be done with a file in a pinch, but using a lathe gives better-looking results.

I screwed everything back together and powered up the mic. The modified mic is clearly better than stock… the high frequencies do seem more extended and better defined. The stock CM90 exhibits a very slight kind of “splatter,” if you will. Make no mistake, my mic does NOT sound as good as a KM84. I didn’t expect it to. But it is interesting, and a little bit fun as well. I think I’ll send these up to another engineer in Nashville to see what he thinks.

The next step in my upgrade path will have to wait a little while. I want to see if I can build a true KM84 amp and see how this sounds when coupled with the modified Nady capsule. An important part of the KM84’s sound comes from its transformer, and the Nady circuit is transformerless. I haven’t been able to find a source for a BV107 transformer (the original part used by Neumann) or a small enough substitute. I understand that Cinemag 2510 will work in this circuit, but I think these are physically too large for a KM84-sized body… I’ll keep you posted.

The completed mic. I’m looking for some finer brass screen for the next one, but this one looks and works pretty good.

A New Microphone

NOTE: This mic is for sale… $230, includes a custom built walnut case. Email me for more info.

It’s always fun to get a new mic in the studio. This one is twice as nice, since I built it myself. It’s based on a typical large-diaphragm cardioid pattern mic from China… identical to most of the ones you see from ADK, Behringer, MXL, etc. This one is different. It uses the stock mic diaphragm, transformer, and metalwork, but the circuitry was completely replaced with higher-quality components from Mouser. I got help from the folks on the Micbuilders groupon Yahoo.

My new mic setup for testing. Stock mic is on the left, modded mic is on the right, in the iso mount

I’ve built a pair of these in the past that were all stock, so I have a baseline to compare changes that I make. This latest mic is better… the difference is very subtle, but I think that I could pick out the modified mic in a blind test. There is a slightly extended bass and more definition overall. This is probably due to the capacitors… the stock mic uses tantalum caps, the mod uses all polyester film and Nichicon electrolytics. I think this probably contributes most to the improvement in the sound.

Some other changes that I’d like to try are some different transformers, though this can be a pretty expensive upgrade with an unknown benefit. Only one way to know for sure. But I’ll likely save that experiment for another mic. Right now, this one is good enough to put directly into inventory to either use or sell. It was a fun build, though mic #2 took me quite a while to finish. I thought I’d popped a JFET, but it turned out to be a bad solder joint on a capacitor that took me forever to track down. All straightened out now, though.

A pair of mics under construction. One of the capsules has lost tension, it was replaced. I’m still having difficulty getting #2 to work… I believe I have a bad JFET caused by me miswiring the transformer.

Making the boards work in the new mic is a trick, since the components are all physically larger, but I was able to coax them into place.

A New Shotgun

Thanks to some series work that I’ve landed in Knoxville, I’ve recently made an upgrade to my mic locker. My workhorse mic, a Sennheiser ME66/k6 combo, is a very good mic… for the price. They can be bought new for around $500. But it’s long been on my list of things that I’d like to improve, if ever I could afford it.

For critical applications, I have a MKH415T that I love. It’s a beautiful old mic, once used by the ORTF (the French equivalent of PBS). But there are some considerations that prevent me using this mic as much as I’d like. Mainly, it’s the fact that 415’s don’t like humidity, and begin to develop self-noise in damp air. Once things dry out, they return to normal, but the unpredictable nature of the mic means that it stays in the box 95% of the time. (According to Sennheiser, the 416 was a later development and uses improved circuitry to eliminate fluctuations in performance from humidity.)

The other soundperson on the series, Raleigh mixer Neal Gettinger, loaned me his 416T to use for the shoot, and it sounds markedly better than the mic I normally use. Thanks to some sales of used gear at Trew, I had a balance that I applied to a brand-new Sennheiser MKH416p48.

It doesn’t seem like much until you plug it in. Physically, it’s a bit smaller and slightly heavier than the 66, so I had to get new mounting clips for my Rycote suspension. Soundwise, though, there’s a big difference in the two. It’s hard to describe in words, but the 416 has a smoother overall quality… the top end is more defined, and the low end seems extended. These differences really show up when you compare the mics side-by-side and switch between them. But almost as important is the familiarity factor… most people know the 416, and it’s been a common player in movie production…. so much so that years ago, when the 416 was discontinued for a model with improved specs, the resulting uproar from the location sound community caused them to put it back into production.

I hate to do it, but I’ll probably sell my 415T to help pay for the new mic. I’ll most likely need to sell the ME66 as well, but I haven’t quite decided yet. The fact that the 66 can be battery powered gives it a slight advantage, since this mic can be plugged directly into any camera without the need of a mixer. Like many true condenser mics, The 416 needs  48 volts phantom power to operate properly, and some  cameras (and even mixers… older Shures are reported to deliver only 18 volts) can’t provide enough voltage.

How To Make Turtle Clips

I can hear you. You’re saying, “What the #%*& is a turtle clip?”… a reasonable response to the above headline, actually. I didn’t know about them myself until recently. A “turtle clip” is a mic clip with a little wire bail over it. The wire is there to keep fabric away from the mic, preventing clothing rustle.

A commercially available turtle clip for a Tram lav

If you’re flush with cash and short on time, you can buy these from B&H for $20 apiece. Or you could make them yourself. All you need are some bits of copper wire, something round (like a dowel or broom handle) to use as a former, a pair of needlenose pliers, and a pair of cutters. Optionally, you can use a soldering iron if you want to get fancy, but it isn’t required. The clips that I made require a bit of Topstik or Moleskin to secure the mic, but they work as well as the ones from B&H.

Any round object will do as a former. The size determines the diameter of the finished mic clip… about a half-inch or three-quarter-inch rod will do. Wrap the wire around the former as if you were winding a spring one and a half turns. It’s easiest to wind a little extra and then clip off the excess wire later.

Starting a turtle clip. Copper wire is wound around a round former, 1 1/2 turns

Now, using the needlenose pliers, bend a half turn of the wire up 90 degrees. Clip off any excess wire and you’re done, unless you want to solder the ends. Soldering only takes a second and does make the finished clips a tad stronger and smoother, but it isn’t required. If you haven’t done much soldering before, this step could be

Bend one of the loops 90 degrees. I used a vise, but pliers can work fine for this.

a little tricky, but it’s very easy with a little practice. (HINT: Heat the wires first, then apply the solder to the wires. Don’t apply solder to the soldering iron, except maybe to help transfer the heat to the wires.)

Once you’ve made a few of these, other variations and improvements will surely come to you…

Snipping off the excess wire. Having a little extra wire makes handling these a touch easier while you make them.

making clips with two bails, for example, or rectangular shapes rather than round. They will get rather bent out of shape with regular use, but they’re easily replaced and cost only a little time. And if you’re too busy to take the ten minutes it takes to make these, I’ll be happy to sell you some that I’ve made… only twenty dollars each!

My collection of homemade turtle clips. They didn't take long to make, and they get easier with a little practice.

Comparing Lav Mics

I don’t have a huge collection of lav microphones, but I’ve tried several different models over the years. All of them work amazingly well, though I’ve naturally developed a preference, and I do have one particular model that I tend to use as my “go-to” mic (which I’ll reveal in a moment).

Some wired lavs- from left to right, unmarked EV lav, evCO90, Sony ECM44b, Sony ECM55b

The problem with comparing different lav mic models is that many wireless transmitters use their own wiring conventions. Lectrosonics uses a five-pin connector (a TA5), while Sony and Sennheiser use a 3.5mm jack… and the two aren’t interchangeable. So while I have a fairly diverse collection of lavs, they aren’t all wired to use the same transmitter. One of these days, I’ll get rid of my other transmitters and go “all Lectro,” but that’s a somewhat expensive proposition.

Two Sennheiser lavs

My lav mic locker includes the following:

  • Countryman EMW (wired for Lectrosonics)
  • Countryman B6 (Lectro)
  • Audio Technica 899 (Lectro)
  • Lectrosonics 119
  • Lectrosonics 152
  • Sennheiser ME102
  • Sennheiser ME104
  • Sony ECM44B (hardwire)
  • Sony ECM55B (hardwire)
  • Sony UWP lav
  • EV CO90 (hardwire)
  • EV MysteryLav- looks suspiciously like a Sanken COS11

These two mics are the ones I use most often... a Countryman EMW and my current favorite, the Audio Technica 899

There is a really good article about comparing several different models of lav mics at Ken Stone’s website- click here. I haven’t done extensive side-by-side comparisons of all the mics that I have, but I’ve got some favorites. I found a good deal on some Countryman EMWs. These are small, rectangular, side-address lavs, similar to Trams, which are kind of an industry standard. But Trams were too expensive and only available new. The EMWs small size and resistance to handling noise are big advantages and I used these for several years. But then I happened to try an Audio Technica 899 during a 3-person shoot… two people wore EMWs, and one wore an 899. While all sounded good, I was surprised at the reduction in room noise when I soloed the 899… there was a significant improvement in the amount of background noise. Since then I’ve managed to purchase a set of three 899s, and these are my favorite mics in most situations.

Any mic with a larger head is generally not my first choice on the set, since most clients would rather hide the mic in the talent’s clothing, even though this means a reduction is sound quality. My Sony 55b almost never gets used for this reason, even though it’s an excellent-sounding mic. My Lectrosonics mics have some rather questionable-looking cables, so I keep them to use as backup mics.

My First Place & the Ambient EMP Eumel

I was recently in Nashville, TN shooting an episode of HGTV’s My First Place. I was glad to finally get the gig… they’d called me a number of times before, and I was always booked. And because of the way things work out on this show, they don’t usually give their crew much notice (less than 24 hrs on one occasion). Scheduling last-minute shoots is difficult… I try to make them work, but I’m often booked. That’s how it’s been with My First Place in the past, so I was especially pleased that I was able to make this shoot work.

I worked with two Nashville freelancers, producer Laura Douglas and DP Chris Conder. Both have been working in and around Nashville for a number of years, and Laura had worked in news, so we all had similar experiences to share. The show is produced by High Noon Entertainment in Colorado. I’ve worked with them before, but this particular shoot was done with an all-local crew… no one flew in for the show.

One of two Ambient EMP 5s transformers that I recently bought. I've been needing these for a long time, and they work like a charm.

I tried out a new piece of gear on this trip… an Ambient EMP 5s eumel. (a eumal–pronounced “oymal–” is German for widget.) It isn’t a very sexy bit of kit, and it’s pretty pricey (about $118 each from Trew Audio) but it’s extremely handy to have. All they are is a transformer built into a nicely machined Neutrik connector. What they do is convert a wireless lav microphone– in this particular case, my Audio Technica 899– into a hard-wired version. Since these were going to be seated interviews, I figured this would be the perfect application. I’m happy to report they work like a charm. I have several mics that are wired for Lectrosonics transmitters, and now I can use these all as hardwires if the job calls for it. In the past, I have used a Sony ECM55b for my hardwire jobs, and while it works great, I have often wished to use a mic with a smaller head– like my Countryman EMWs or my ATs, since the Sony is a little harder to hide. My Ambient EMPs give me more options, and options are always nice to have on the set!

The guys that were buying their first place had a budget of $140K, and wanted a minimum of 1,000 square feet. Nashville is a nice town, but the real estate prices are pretty steep for most people. (In contrast, we’re looking at a 2,800 square foot house here in Chattanooga, and the selling price is $192K. That’s nearly 3x the house for about $50k more dollars. There’s just no music industry here, unfortunately.)

Producer Laura Douglas interviews first-time homebuyers Bret Marchbanks and Daniel Sircy for HGTV's My First Place. Chris Conder on camera.

The only bad part about the shoot was the drive home. I work as a local in Nashville for one-day shoots, so  had to drive home that night. We finished the interviews at 10PM local time, and since Nashville is in a different time zone than Chattanooga, I pulled into my driveway at 2AM. But I’m looking forward to working with them again soon.

More Fun With 5.1… The Double Mid-Side Technique

After my last post on an inexpensive 5.1 workflow, a reader (Peter Tooke… thanks, Peter) advised me to look into the double mid-side technique. This is a method used for 5.1 surround sound recording that I’ve seen used on feature films, and while it can be a little complex to wrap your head around, it’s pretty neat.

The “mid-side” mic technique is a method of recording stereo using a cardioid mic facing forward (the “mid” mic) and a bidirectional, or “figure-8″ mic facing left and right (the”side” mic). These mics require a little processing at the mixer, though, before we get a stereo signal.

Schoeps has several hardware options to support a double mid-side setup

The mid mic is panned to the center, but the side mic is split into two equal signals. You can do this analog using a transformer-balanced splitter, or digitally by copying the input to duplicate channel. Pan one of these mid signals hard left, and pan the other hard right, but… and this is the key… invert the phase on the right channel.

The beauty of the mid-side technique is that if the left and right channels get summed together for a mono signal, you get no phase cancellation between the two signals. We used this technique in the early days of television, when some of the sets were mono and some were stereo. Using mid-side stereo, both stereo and mono televisions sounded fine. (More details about the mid-side technique are here.)

The double mid-side technique is an expansion of the mid-side technique. By simply adding a rear-facing mic we now have a system that can generate five channels of audio using only three tracks. Use a shotgun for the main mid mic, add a bidirectional mic for the side signal, and a cardioid rear-facing mic. The side signal is shared between the front and the rear mics. Each mic is recorded on its own track.

Decoding the three signals into a 5.1 mix is straightforward. The shotgun becomes our center channel, shotgun plus the mid (split, panned left and right, and phase-reversed for the right side)  becomes our left and right front signal,  rear cardioid plus the mid (split, panned left and right, and phase-reversed for the right side)  becomes our left and right rear signal… pretty neat, eh? And like the standard M-S stereo technique, the signals can be summed to mono without phase error.

The Schoeps double mid-side recording solution has the advantage of the entire rig being able to fit inside a zeppelin.

Shoeps has a good bit of information about double mid-side technique on their website, including some elegant hardware solutions for implementing this system in the field. Hang on to your wallet, though, cause this ain’t a Chinese knockoff… it’s some serious hardware that is priced accordingly.

Schoeps even has a free double mid-side plugin that decodes the three signals for a double mid-side system. Order it here.

A screenshot from the free Schoeps double mid-side plugin